Broad band television antenna



June 27, 1950 J. s. BROWN BROADBAND TELEVISION ANTENNA Filed June 19, 1947 Patented June 27, 1950 y 2,513,071; ,n BROAD BAND TELEVISION ANTENNA Jghn'sfefown, (imago, m'gjsegiitjy mme assignments, to Andrew Corporation; ai corpo;

ration of Dlinois j Application .nine 19, ieiaserial No. 759,612;L

4eme. or ziejmc.

'Aftelevision receiving antenna for satisfactory results must :delivera signal` to the receiver of suicient' strength to operat'eit satisfactorily in cludng "proper"`operation of the synchronizing circuitand furthermore shouldfdeliver a signal which is Tree frorndouble imagesv or ghosts To e'ect'max'imum power transfer'to the receiver the impedance of the antennalinustmatch'the impedance 'of theI transmission linefwhich connects it to the receiver.' T hus the 'antenna resistance is predetermined at the standard'inputimpedance ftelevisfion FM rece`iver,' 'and the re`` actance of the' antenna 'should b e a vminimum 'Ifhe antennashould` have sufficient directional properties"sthatit may `ibe orientedl so as to eliminate the ghostsl `or` Vvsecondary images caused lby energy reaching the receiving antenna after reection'-fro`msome'objectf It* is furthermoreitdesirable in an antenna of this'kind/to have 'its sizleandappearance such:

that it will not be objectionable When'in'stalled' on homes or apartments. The antenna furthermore should be-YhorizontallyV polarized since this is the standardprovided'fcrv t'l isilon transmit- .'Tj' .'"f "."IL' i" It, therefore, is an object of the present invention to provide an improved television'receiving antenna which will satisfactorily operate on allV the television channels now inuse.

' A frther'object'of'the presentiuvention is to provide' animprvedtelevision receiving antenna Having `airnpl'einounting means vand capable of b'ing'rot'ated r"'6r1e"`tedi" A still further'objectffof the present invention is toprovide an improved `television receiving antenna which is relativelyfeconomical to manufacture'and which has a suitable size and appearance f or installation on homes or apartments.

Still another object of the present invention is to provide an"'i1r"1proved'television'l receiving antenne, which'is horizntally'polrized and which has-'s'ch electrical characteristics toeieetfthe` maximum power transfer of energy toi'tlleftelevision and FMreceiver;VT f 'f' E 2 Other and further objects of the present invention subsequently" will becomeappa'ren't by reference tofthe following `description taken` in, conjunction with n "thevv accompanying drawings wherein: i; Figure 1 is a perspective view of an antenna constructed in accordance with the' principles. of the present `invention; JL

Figure 2 isa graphical representation of the eiiency of the present antennaoveruawide range ofufrequencies; "Figure 3`is'a `graphical representation of the characteristics which'rniniinize .a reflection. of the incident signal whichptherwise mi'ghtcausea ghostimage; j figure 4 isa horizontal directivity pattern at one frequency of operation; andi if' i Figure 5 is'anther horizontal directivity pattern atanother operatingfreque'nc'y. "i A' Referring to' the drawing it will'be seen that there hasv been show'n in"Figur`e"1 an 'antenna structuresupportedf'by a tubular member .II which is adapted to -be slipped overvrzapipe'or tubular member and secured Aimproper oriented position by a fasteningor set'screwrllz.' The tubular member I I supports'a channelmen'bei''l which carries a plurality of insulators"`I'4;" Three ofthe insulators I4 Vsupporta triangular'iplatei which in turn carries Va plurality of iantenna; rods IB, The antenna'rods I6 areplace'd infan for; mationl and each rod 'held in 'positionA by'a clamping member I'I secured by screws'pl'.' yIt will be appreciated that each of theinsu'lators I4" is formed in a plurality of sections, onesectionf extendingl below the channel I3,"another"se'ction' extending betweenthe 'channel I3 and theplate I5' and a third section extending aboveith'e'plat'e;` I5 L. Suitable apertures are formed in thechannel I3 andv each of the plates 'I5 to provideadequatey insulation between the plates and th "fastening bolts I9Which hold the' assembled'insulators" and plates in position. The channel I 3 ycarries .a sup--v port- -plate -2I secured -inx Aposition 0'by -screw.s-?r2 The outerfextremityof theplate` 2-I carriesinsu-y latex-bars 23-forrclamping and-holdfing-fin position by means of screwsl y2 4= f atransmissionlinee! zw ff In-fone'f'embodiment theftrianglanlsectors: I5 had la radius offiive 'and"sevn-eighths'finches ThS'e tla'guIrTm l01" "dt'l 'il 5*? WT mounted on insulators'whichsuppted 'the' plates" two linches above the charinelsupprt?p'l'ate- I 3. Each 'ofthe rods I6` extendd`bet'fond -thef'outer edge of the plate I5 lapproximately 'i'lftyfour' inches. .1,

-. It lvfill be noted that ve elements or rods I6 Were provided -for eachY sector lI5 since a fewer" "number would not providethe desired-stem'dingwave ratio.` The sector plate-I5 inthe particular embodiment referred to coveredan angle.oiiitnv two degrees so that the elements I6 coverV an angle of forty-five degrees'. j v l By referringto Figure 2 it will be noted that the antenna constructed in accordance with they` v loss introduced by the antenna of Figure l. This mismatch loss is expressed in decibels .whichjs assembled by the use of simple tools such as a the ratio of the power actually transferred from the antenna to the transmission line compared 1 to that power that would be delivered to the line if the line and. the antenna were perfectly matched. The relatively. at characteristic of curve A which corresponds to. thatof the structure shown in Figure 1 clearly showsthe superiority over curve B which corresponds to thefcurve of a folded dipole. i Y

. By having the antenna of Figure 1.- supported so that it may be oriented,.itli s' possible to eliminate ghos signals whichare caused by the reflection of transmitted energyfrom someobject. Ghost signals can also be vcaused by. rereflection in the transmission line. Si-nce the irn- `pedance match betweenthe line andthe termi- .nals of the television receiver can never 'bemade perfect, a portion of the signal is reflectedatthe. f jreceiver terminals which travels back-.unibe line and is re-reilectedatthe antenna to again re- 1turn tothe receiver in the form of a second 4image displaced from .the first. The percentage .0f the lreceived signal lwhich will lbe reflected'back at the, line from .the receiver therefore, .depends on the degree of mismatch between the Yreceiverinput impedance and the. transmission. line impedance. .The co-eicient of reflection expresses this re-reection characteristic, which. might cause a ghost image.

Figure 3.shows a comparison o-f the co-efcient. of reflection of a folded dipole by curve D as compared to the curve-C which illustrates the char-7 acterlstic of the antenna of Figure -1. Againv it will be noted that over-the frequency range given in the graph, the curve C :is much flattepand lower than curve D, thus indicating .that arelatively good impedance match has been-obtained. between the antenna and the `transmission line.r As previously mentioned .the ,orientation of the antenna is employed for eliminating-the.ghost images where the signal has been reflected from otherobjects. Figure 4 graphically portrays .the

i directivity' characteristic ofthe antenna of Fie-j ure 1 at a frequency of 82 mc. Throughoutthe lower lfrequency ranges and over the major portion Yof the operating range ofthe antenna, the

\ antennahas the characteristic figure B directivity v ulate electrically a plane.

a double fan shaped configuration formed by radial copper wires or tubes supported by a sheet copper fan or sector. Favorable electrical characteristics consistent with mechanical and ecocomponents -of the antenna are arranged to be screwdriver and wrench, the mechanical strength is adequate and no breakage or loosening of the parts occur. l y y AWhile in the commercial embodiment illustrated, a certain number f rods. and certain angles have been mentioned, other embodimentsl have been employed including a greater number of rods and a greater angle up to one hundred and twenty degrees for each sector. It, therefore, will be appreciated that for the frequency ranges mentioned the rods have been employed to sim- Where the frequency range is up in the microwaves, it is possible to dispense with the rods and to utilize the two sectors of proper dimensions. It, therefore, will be Iappreciated that these and other variations may be made in the antenna structure. i

While fcr'the purpose of illustrating anddescribing the present invention, 'a preferred embodiment has been shown in ,the drawingait `is to be understood that the invention is not to be limited thereby since such variations in the conj struction and in the components employed are tor supportmembers above said base in diamet-v patterh similar to thatshown'in Figure 4.` At

the highfrequenc'y bandv the directivity pattern deviates from the figure \8" by' the formation of lobes so that the'pattern appears as rillustrated in Figurev 5. It will be notedg'however, that the nulls of the --antenna are still sufficiently sharp to serve in reducing ghost images. v

In thecommercial embodimentofthe antenna l illustrated vin Figure 1.,the transmission-line 25 j consists of atwin lead extruded polyethylene insulated transmission line sixty feet in length having van impedance of 300 ohms. The conductors of the transmission line 2,5` are connected to the apexes of the sectors I5 -.by suitable lugs 26 he1d in position by screws 21.y 'f

inaccordance with the 'present inventionfthere 'From the foregoing it'w'in be .appreciated that l contemplated as may becommensurate with the spirit and scope of the vinvention set forth in the accompanying claim. l

lWhat Ide'sire tofprotect by United States Letters Patent is claimed as follows: A horizontally polarized directional antenna for television reception .comprising a horizontal base, a -pair of horizontal sector support members, a plurality of insulators supporting said secrically opposite positions, a plurality of rods removably mounted on said -sector support members, said rods extending in radial formationy at equal interi/ alsof not more'than 12, and means for connecting a line conductor to the apexvof each sector support member. f

REFERECES ,CITED y The following referencesv are of record inthe le of this patent: f 'Y f UNITED STATES PATENTS y 'j Date Antennas for Television Receivers, by`E.No l1, published in Radio News, May 1945, pages 40-42,

and132L f' i i Prospectus released byxfAndreWiCo;,;v -B;ulletin 45, copyright obtained October 14, 1946.

JOHN s. BROWN i 

